Non-corrosive antifreeze composition



United States Patent 3,231,502 NON-CORROSHVE ANTIFREEZE COMPOSITION .ioei D. Watkins, Gayle D. Edwards, and JohnG. Willard,

Austin, Tex, assignors to Jefferson Qhemical Company,

lino, Houston, Tex., a corporation of Delawarev No Drawing. Filed AphlZ, 1961, Ser. No. 102,408

8 Claims. (Cl; 25275) This invention relates to improved antifreeze compositions. More particularly, this invention relates to substantially non-corrosive antifreeze compositions.

It is well known that uninhibited aqueous antifreeze solutions may cause corrosion of metals during service. Thus, an uninhibited aqueous antifreeze solution may be corrosive with respect to brass, copper, solder, steel, cast iron and cast aluminum in heat exchange systems such as the. cooling systems of internal combustion engines. Solder, steel, cast iron and cast aluminum are particularly susceptible to corrosion.

In copending Robert R. Reese application, Serial No. 831,726, filed October 5, 1959, and entitled, Antifreeze, now abandoned, there is disclosed a class of antifreeze compositions containing novel corrosion inhibitors which materially inhibit corrosion of materials. In particular, the Reese application discloses and claims antifreeze compositions consisting essentially of a water soluble liquid alcohol freezing point depressant, a sodium borate and a magnesium borate. While the results obtained in compositions of this nature are generally satisfactory, a special problem is encountered when the antifreeze composition is added to water containing sulfate ions and when the inhibitor composition consists of a mixture of sodium tetraborate with magnesium metaborate, in that moderate corrosion of solder, steel and cast iron may occur. It has now been discovered that this problem may be overcome through the further modified antifreeze compositions of the present invention wherein an alcohol type freezing point depressant has incorporated therein inhibiting amounts of an inhibitor composition consisting essentially of magnesium metaborate, sodium tetraborate and an additive selected from the group consisting of sodium metaarse nite, sodium mercaptobenzothiazole, and mixtures thereof. Compositions of this nature are single phase antifreeze compositions which are foam-resistant, compatible with rubber hosing, and which, moreover, provide superior corrosion protection to metals.

Thus, it has been found that sodium metaarsenite, sodium 1nercaptobenzothiazole, and mixtures thereof, act synergistically in combination with sodium tetraborate and magnesium metaborate to inhibit substantially completely corrosion of solder, steel and cast iron when these materials are contacted with sulfate containing aqueous solutions of antifreeze compositions of the present invention.

The freezing point depressants of the present invention include any of the water miscible liquid alcohols such "as monohydroxy lower alkyl alcohols and the liquid polyhydroxy alcohols such as the 'alkenylene and dialkyleiie glycols. Specific examples of the alcohol contemplated herein are methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and mixtures thereof. The freezing point depressant should generally constitute between about 10 and 100 volume (vol.) 'perc entof the novel antifreeze composition. A preferred glycol is'ethyle'ne glycol, which as sold commercially, often contains a small amount, up to 10% by weight, of diethylene glycol. The term ethylene glycol as used herein is intended to include either the pure or commercial compound. This is also true of the other freezing point depressant alcohols 'contemplated herein.

One of the inhibitor components of the present invention is magnesium metaborate. The quantity of magnesium metab'orate to be employed in the antifreeze compositions of the present invention should generally be between about 0.05 to 2 wt. percent based on the Weight of the inhibited alcohol freezing point depressant. More preferably, 'the composition will contain from about 0.1 to about 1 wt. percent of magnesium metaborate.

Another component of the inhibitor composition of the present invention is sodium tetraborate and a preferred sodium tetraborate is sodium tetraborate decahydrate (borax) or sodium tetraborate pentahydrate. The quantity of sodium tetraborate to be employed in the antifreeze composition of the present invention is desirably in the range between about 0.1 and 5 wt. percent, based on the weight of the inhibited alcohol freezing point depressant. More preferably, from about 1 to 4 wt. percent of the sodium tetraborate will be employed.

A third component of the inhibitor composition of the present invention is sodium metaarsenite. It is generally desirable to utilize from about 0.1 to about 1 wt. percent of sodium metaarsenite, based on the weight of the inhibited alcohol freezing point depressant. More preferably, from about 0.2 to about 1 wt. percent of sodium metaa'rsenite is employed.

A fourth components of the present invention is sodium mercaptobenzothiazole. It is generally desirable to utilize from about 0.05 to about 1 wt. percent of sodium mercaptobenzothiazole based on the weight of the uninhibited alcohol freezing point depressant. More preferably, from about 0.1 to about 1 wt. percent of sodium mercaptobenzothiazole will be employed.

Preferably, a mixture of sodium metaarsenite with sodium mercaptobenzothiazole is employed.

The antifreeze composition, as prepared, may contain a minor amout of water (e.g., from about 1 to 5 wt. percent of water).

When the antifreeze composition is to be utilized in 'a heat exchange system, it may be combined with water in any and all proportions. When aqueous solutions of the novel antifreeze are to be used as coolants in automotive cooling systems, the water miscible liquid alcohol freezing point depressant should generally constitute at least about 10 tel. percent, preferably between about 20 I and 65 vol. p e r ecrit or the aqueous antifreeze solution.

The corresponding water content should therefore constitute less than about vol. percent, preferably between about 35% and 80% by volume of the aqueous antifreeze solution,

, ASdIldlCfitGd, the present invention is particularly usefulwhen the water contains more than about 50 parts per million of sodium sulfate (e.g., from 50 to 300 ppm. of sodium sulfate).

It is to be noted that the freezing point of the aqueous antifreeze coolants is substantially determined by relative component quantities and particular freezing point depressant used therein. For example, in an aqueous ethylene glycol solution a minimum freezing point'of approximately is obtained with about 65% ethylene glycol by volume.

In preparing the novel antifreeze compositions and aqueous solutions thereof, the m agne s iu minetabofate is conveniently formed in situ by adding boric acid and magnesium oxide in the mole ratio of about 3:06zl to a water soluble liquid alcohol. The resultant solution is mixed at a temperature of between about 50 and 250 F;, preferably between about and 200 F. until a clear"homogeneous'solution is formed. This in situ "reaction is normally conducted at atmospheric pressure. However, if the reaction temperature exceeds the boiling point of the freezing point depressant, superatmospheric pressure is applied to maintain the freezing point depressant in a liquid state. In addition to the formation of the magnesium borate product, water is also an incidental product of the reaction. Water, however, is not an essential ingredient of the antifreeze concentrate as far as corrosion inhibition and anti-foam properties are concerned. Sodium tetraborate may be added to the resulting solution as a solid with agitation until completely dissolved. Sodium metaarsenite may be added as a 40% aqueous solution prepared by reacting one mole of arsenic trioxide with two moles of sodium hydroxide dissolved in water. Sodium mercaptobenzothiazole may be added as a 50% aqueous solution. If desired, water may then be added to the antifreeze concentrate to form aqueous solutions thereof.

Among the metals that will be protected by the disclosed antifreeze composition even in the presence of aqueous sulfate containing solutions containing up to 300 p.p.m. concentration of sodium sulfate ions are brass, copper, steel, solder, cast iron, and cast aluminum.

The invention will be further illustrated by the following specific examples which are given by way of illustration and not as limitations on the scope of this invention.

Example I This example illustrates a method of preparing a base solution (Composition No. 1) containing ethylene glycol, magnesium metaborate, and sodium tetraborate to which sodium metaarsenite and sodium mercaptobenzothiazole can be added to form the novel antifreeze compositions.

To 1600 grams of commercial ethylene glycol containing a maximum of 5 wt; percent diethylene glycol and about 216.8 grams of water, there was added, with agitation, 20.2 grams of boric acid. The resultant mixture was heated to a temperature of about 130 F., and about 6.6 grams of magnesium oxide was added to the mixture with agitation. The temperature was increased to about 200 F. for about 1.5 hours. About 156.4 grams of sodium tetraborate pentahydrate was added to the resultant solution with agitation, and the agitation was continued until a clear homogeneous solution was formed.

About 8000 grams of ethylene glycol was added to the resulting composition, on cooling, to provide a product having the following composition:

Ingredient: Wt. percent Ethylene glycol 96.00 Magnesium metaborate 0.18 Sodium tetraborate 1.08 Water 2.74

Example 11 Three antifreeze compositions were prepared by the method of Example I except that sodium metaarsenite or sodium mercaptobenzothiazole, or a mixture thereof, was added, together with the sodium tetraborate pentahydrate; the sodium metaarsenite and sodium rnercaptobenzothiazole being added as 40 and 50 wt. percent of aqueous solutions respectively. The modified thus-prepared formulations have the following composition:

The synergistic corrosion inhibiting action of the sodium tetraborate-magnesium metaborate inhibitor when used in combination with sodium metaarsenite or sodium mercaptobenzothiazole, or a mixture thereof, is-illustrated stopper and fit on the container.

by the following corrosion test. This corrosion test. is well known and accepted in the industry as a method of evaluating the effectiveness of corrosion inhibitors in antifreeze solutions. It simulates conditions under which corrosion of oxidizable metals is frequently encountered in automotive engine cooling systems containing antifreeze compositions.

In the test procedure, specimens of metals typical of those present in automotive cooling systems are totally immersed in the test antifreeze solution for 336 hours at 180 F. with aeration. The corrosion-inhibitive properties of the test solution are evaluated on the basis of the weight losses incurred by the specimens. Each test is run in triplicate, and the average weight loss is determined for each metal.

The metal specimens used in this method include brass, copper, solder, steel, cast iron, and cast aluminum. Each specimen is 1 by 2 by inches in size except the iron and aluminum specimens which are Ma inch thick. A inch hole is drilled in the center of each specimen. The iron and aluminum surfaces are sanded with a 150 grit aluminum oxide paper. All specimens are scrubbed with a moistened soft bristle brush and pumice powder until a water break-free surface is obtained. The specimens are then rinsed with water and acetone, dried and weighed.

The metal specimens are assembled as follows:

Cover a 10-24 brass machine screw with a thin-walled insulating tubing, having an 0.1). of less than inch. Two brass legs are prepared from sheet stock to a size of 1 by 2 by inches. A r-inch hole is located with the center inch from the top and inch from each side. Mount specimens on the insulating screw in the following order: brass leg, copper, solder, brass, steel, cast iron, aluminum, brass leg. Specimens are separated with inch spacers, having an ID. of 4 inch and an OD. of less than 0.40 inch. Insulating spacers are used between the legs and specimens and between brass and steel. Brass spacers are used between copper, solder, and brass. Steel spacers are used between steel, cast iron, and aluminum. The nut shall be tightened firmly to assure good electrical contact.

The test is conducted in a 1000 m1. tall-form, lipless beaker, fitted with a No. 15 rubber stopper which has holes to accommodate a condenser and aerator tube. An air condenser of glass tubing, 20 inches in length and an ID. of 10 mm. is used. An aerator tube of the gasdispersion type with 12C porosity size is used (Corning Glass Works, 44 Crystal Street, Corning, New York, tube No. 39533, or equivalent). The test water is a synthetic water containing 100 p.p.m. of sodium chloride and 300 p.p.m. of sodium sulfate in distilled water. Antifreeze solutions are composed of 1 part by volume of antifreeze to 2 parts of test water.

The procedure for conducting the test is as follows:

Place the test packet of metals at the base of the container with the 2 inch dimension in a vertical position, and the legs resting on the base of the container, supporting the specimens in a position inch from the bottom. Assemble the condenser and aerator tube in the rubber Place the container in a water bath which is maintained at a temperature of li2 F. The water bath should be of suflicient depth to immerse the test container to the depth of the test solution. Adjust the aeration rate at ml. per min., using a flow-meter or other suitable device. Continue the test for a period of 336 hours. Maintain the. volume by periodic additions of distilled water.

At the end of the test, remove and scrub the specimens lightly with a moistened, soft bristle brush to remove loosely held corrosion products. Tenacious products may be loosened with a scraper. Subject the metals to an additionalcleaning procedure as fol-lows:

Iron and steel.Electrolytic cleaning. in a 5% by weight sulfuric acid solution, containing 2 ml. of organic inhibitor (i.e., Rhodine) per liter of solution. The specimen is made the cathode with a lead or carbon anode. The temperature of the solution is 165 F. A cathode current density of 20 amp/sq. dm. is used for a period of 3 minutes. After removal, the specimens are scrubbed ligthly with a soft bristle brush and pumice.

Copper and brass.-Immerse in a 20% solution of hydrochloric acid for 30 seconds at room temperature. Scrub lightly with a soft bristle brush and pumice. Repeat if necessary to produce suflicient cleaning.

Aluminum.--Dip for 5 minutes in a solution, containing 2% chromic acid and 5% phosphoric acid, which is maintained at a temperature of 175 F. Scrub lightly to remove any loose film, rinse and dry. If necessary, follow by a 1-minute immersion in concentrated nitric acid and repeat the previous steps.

SIder.-Immerse specimens in a boiling 1% acetic acid solution for minutes. Very gently remove any loosened film with a bristle brush.

Each specimen is finally rinsed well in water and then alcohol or acetone. Dry and weigh to the nearest milligram. A weight correction for each cleaning procedure can be determined by running new specimens in triplicate through the same steps given above. This correction should be subtracted from the weight loss determined for each metal specimen.

The four above-identified antifreeze compositions of Examples I and II designated Nos. 1, 2, 3 and 4 were subjected to the above test. The results are reported below in Table II.

TABLE II Corrosion Wt. Loss, mg.lsq. in. Formulation Brass Copper Solder Steel Cast Fe Cast Al As can be seen from the above table, Compositions 2 to 4 of the present invention significantly reduced the corrosiveness of the antifreeze with respect to solder, steel, and cast iron without significant adverse effect upon corrosiveness with respect to brass, copper, and cast aluminum. It will also be apparent that Compositions 2 and 3 will be particularly useful in cooling systems where corrosion of aluminum is more critical than corrosion of cop per or solder and that Composition 4 will be particularly useful in cooling systems where aluminum is either absent or used only in non-critical areas.

What is claimed is:

1. An antifreeze composition adapted to be added to Water consisting essentially of a water soluble liquid alcohol freezing point depressant, between about 0.05 to two weight percent of magnesium metaborate, from about 0.1 to about five weight percent of sodium tetraborate and a member selected from the class consisting of from about 0.1 to one weight percent of sodium metaarsenite, from about 0.05 to about one weight percent of sodium mercaptobenzothiazole and, within said weight ranges, mixtures of said sodium metaarsenite with sodium mercaptobenzothiazole.

2. An antifreeze composition as in claim 1 wherein the liquid alcohol freezing point depressant is ethylene glycol.

3. An antifreeze composition adapted to be added to water consisting essentially of ethylene glycol, between about 0.1 to one weight percent of magnesium metaborate, between about 0.1 to about four weight percent of sodium tetraborate and a member selected from the class consisting of between about 0.2 to one weight percent of sodium metaarsenite, between about 0.1 to one weight percent of sodium mercaptobenzothiazole and, within said weight ranges, mixtures of said sodium metaarsenite with said sodium mercaptobenzothiazole.

4. A composition as in claim 3 wherein the member is sodium metaarsenite.

5. A composition as in claim 3 wherein the member is sodium mercaptobenzothiazole.

6. A composition as in claim 3 wherein the member is a mixture of sodium metaarsenite with sodium mercaptobenzothiazole.

7. An aqueous coolant consisting essentially of between about 20 and volume percent of an antifreeze composi tion and between about 35 and 80 volume percent of water, said water containing from about 50 to about 300 ppm. of sodium sulfate, said antifreeze composition consisting essentially of a water soluble liquid alcohol freezing point depressant, between about 0.05 to two weight percent of magnesium metaborate, between about 0.1 to about five weight percent of sodium tetraborate and a member selected from the class consisting of between about 0.1 to one weight percent of sodium metaarsenjte, between about 0.05 to about one weight percent of sodium mercaptobenzothiazole and, within said weight ranges, mixtures of said sodium mercaptobenzothiazole with said sodium metaarsenite'.

8. An aqueous coolant as in claim 7 wherein the water soluble liquid alcohol freezing point depressant is ethylene glycol and the said member is a mixture of said sodium metaarsenite with said sodium mercaptobenzothiazole.

References Cited by the Examiner UNITED STATES PATENTS 2,373,570 4/1945 Keller 252391 XR 2,803,604 8/1957 Meighen et al. 252 2,834,735 5/1958 Woodle et a1. 25274 2,960,473 11/ 1960 Meighen et al. 25275 3,015,629 1/1962 Truitt 25275 3,030,308 4/1962 Agnew et a1. 25274 3,046,230 7/1962 Berger 25275 JULIUS GREENWALD, Primary Examiner. 

1. AN ANTIFREEZE COMPOSITION ADAPTED TO BE ADDED TO WATER CONSISTING ESSENTIALLY OF A WATER SOLUBLE LIQUID ALCOHOL FREEZING POINT DEPRESSANT, BETWEEN ABOUT 0.05 TO TWO WEIGHT PERCENT OF MAGNESIUM METABORATE, FROM ABOUT 0.1 TO ABOUT FIVE WEIGHT PERCENT OF SODIUM TETRABORATE AND A MEMBER SELECTED FROM THE CLASS CONSISTING OF FROM ABOUT 0.1 TO ONE WEIGHT PERCENT OF SODIUM METAARENITE, FROM ABOUT 0.05 TO ABOUT ONE WEIGHT PERCENT OF SODIUM MERCAPTOBENZOTHIAZOLE AND, WITHIN SAID WEIGHT RANGES, MIXTURES OF SAID SODIUM METAARENITE WITH SODIUM MERCAPTOBENZOTHIAZOLE. 